I have both a physical copy of this book and the digital version. I must say I really love it. The book includes wonderful images of so many periods of writing, I can sit looking through them for hours, learning much, without even reading the accompanying text. The text is an excellent overview, with an introduction giving an account of the history of Western writing (including Latin and Greek quotes on the matter -- of course it assumes you can read Latin!)
Given my fear of touching the original without quite clean hands, the PDF may prove very useful.